That seemingly innocuous morning ritual of grabbing a takeaway coffee could be introducing hundreds of thousands of tiny plastic particles directly into your body, according to new scientific research. A study has found that disposable hot beverage cups, particularly those made of plastic, shed a startling amount of microplastics when filled with a hot drink.
The Scale of the Problem: Billions of Cups, Billions of Particles
The research, co-authored by Xiangyu Liu, a Research Fellow at Griffith University's School of Environment and Science and Australian Rivers Institute, paints a concerning picture of our global coffee habit. The study, published in the Journal of Hazardous Materials: Plastics, highlights that an estimated 500 billion takeaway cups are used every year worldwide.
In Australia alone, the figures are staggering: 1.45 billion single-use hot cups and roughly 890 million plastic lids are consumed annually. The central finding of the research is that heat is a primary driver of microplastic release from these containers, with the cup's material composition playing a critical role.
What Are Microplastics and Why Should We Care?
Microplastics are plastic fragments ranging in size from a speck of dust (about 1 micrometre) to a sesame seed (5 millimetres). They can originate from the breakdown of larger plastic items or be shed directly from products during everyday use.
Currently, scientists lack conclusive evidence on exactly how much microplastic accumulates in the human body or the definitive long-term health impacts. Studies are challenging due to contamination risks and the difficulty of measuring such tiny particles in tissue. However, the pervasive presence of these particles in our environment, food, and drinks makes understanding their sources a pressing concern.
Heat and Material: The Critical Factors in Microplastic Release
The research team first conducted a meta-analysis of 30 existing peer-reviewed studies. This analysis confirmed that as liquid temperature rises, so does microplastic release, with reported levels varying from a few hundred to over 8 million particles per litre.
To test this in a real-world scenario, the scientists collected 400 coffee cups in Brisbane, comprising both all-plastic polyethylene cups and paper cups with a thin plastic lining. They tested them at cold (5°C) and hot (60°C) temperatures.
The results were revealing:
- Material Matters: Plastic-lined paper cups released fewer microplastics than pure plastic cups at both temperatures.
- Heat Triggers Release: For all-plastic cups, switching from cold to hot liquid increased microplastic shedding by approximately 33%.
Using high-resolution imaging, the researchers discovered that all-plastic cups have much rougher inner surfaces compared to lined paper cups. This textured "peak and valley" structure makes it easier for particles to break away, a process accelerated by heat, which softens the plastic and causes expansion and contraction.
The study calculated that if a person drinks 300 millilitres of coffee daily from a polyethylene cup, they could ingest an estimated 363,000 pieces of microplastic annually.
How to Manage Your Microplastic Exposure
You don't necessarily have to abandon your takeaway coffee, but you can make smarter choices to significantly reduce potential exposure:
- Opt for a Reusable Cup: The best choice is a reusable cup made from stainless steel, ceramic, or glass, as these materials do not shed microplastics.
- Choose Paper Over Pure Plastic: If you must use a disposable cup, plastic-lined paper cups are generally a better option than pure plastic ones, though neither is microplastic-free.
- Mind the Temperature: Since heat is the key trigger, avoid putting boiling liquids directly into plastic-lined containers. Asking for your drink to be slightly cooler before it's poured can reduce physical stress on the plastic and lower particle release.
By understanding the interaction between heat and material, both consumers can make more informed choices and manufacturers can be guided towards designing safer, more sustainable products for our daily routines.
